The Stuff You Should Know Doin’ Science Playlist: How X-Rays Work

19:56Chuck Bryant:Look at him over there. So here we are in France in this cave. Tuk Tuk has his hand up against the cave wall, as you'll see. And in his other hand, he's got that little straw filled with pigment, red pigment. He's blowing it on his hand, right? Sure. and now that he moves his hand away, there's the outline of his hand. It's called a stencil, right? Exactly. He's just made an early stencil. He's like a Banksy, basically. Yeah. Like a caveman Banksy. But if you look at the back of Tuk Tuk's hand, don't get too close, but look at the back of his hand. Yeah. It's covered in red pigment, right? Yeah.

20:31Chuck Bryant:So if you want to equate this to an x-ray, the hand absorbed all of that pigment. Right. And the stuff that passed through left the picture on the cave wall. That's kind of what happens with an x-ray. Except with an x-ray photograph, the x-ray photons are absorbed by the denser calcium-rich bones. Yes. And they pass through the softer tissue. So the picture that we have is the outline, the silhouette of the bones. Because the x-rays made it through the tissue. Didn't make it through the bones. They made it through the tissue and onto the x-ray plate, which absorbed the picture in negative. That's right.

21:13And I'm glad you said picture because that's all it is. On the other side of the human being, you know, they're shooting the x-ray at. There's a camera. And you're just going to get a regular negative. And they could make it a positive, but they leave it as a negative because you really don't need the positive image. Right. And that's what they'll put on that little screen to show you your cracked femur.

21:36Chuck Bryant:Exactly. and they can see the crack because some of those x-rays will make it through the gap. That's right. Right? So all you're seeing is the result of x-rays that made it through the tissue were absorbed by the bone, so those don't make it to the plate. The ones that make it to the plate cause the chemical reaction that gives you your negative, your x-ray. And it's pretty simple, really, like if you think about it, at least in principle. it's also extraordinarily difficult to conceive of but if you if you understand like the principle behind it it makes uttering complete sense yeah and it's a pretty focused uh shot that they're using there it's not like they don't fill the entire room with x-rays you know they've got a thick lead shield around the whole device and it you know contains everything it's got a little small window that's just gonna let that narrow beam pass through a series of filters and basically hit you wherever they wanna hit you.

22:34Chuck Bryant:Yeah, and the reason that they use lead is because lead is an extremely dense element, yes. Right? Sure. Oh God, I hope so. With a very high atomic number, which means it can absorb tons of energy, right? Yeah, that's why you're gonna wear a lead apron. If you're getting your skull done, you're probably gonna and wear an apron on your chest, let's say. Sure, so this lead is being bombarded with X-ray photons and electrons, and it's just taking it, it's fine. And it's not being able to, it's not able to pass through because it doesn't have high enough energy. But yes, when they put that little window in the X-ray generating machine, it passes right through there in a concentrated beam.

23:18Chuck Bryant:And Chuck, let's talk about the machine, right? So, and this is basically what we use as X-ray machines is essentially what Rutgen was made, was experimenting with when he accidentally discovered them. Because if you look for x-rays, they propagate naturally, but I think 20 % of the x-rays on Earth come from humans. Oh, really? Yeah, we generate a lot of x-rays. They don't come, you don't find them normally on Earth. They're coming from outer space to us, hence x-ray astronomy. But the ones here on Earth that are generated on Earth, it's not like rocks put out x-rays or something like that. Right.

24:00Chuck Bryant:We do. We humans. We do. Humans and lead aprons put out x-rays. And they use this machine like Röntgen main. Yeah. What you have in the machine, you have an electrode pair, a cathode and an anode, and that's inside a good old-fashioned glass vacuum tube. Right. Which it's amazing how vacuum tubes are still like the best way to do many of these things. Well, it allows things to travel at the speed of light easily. That's right. and it allows guitar amps to sound great. I didn't know these vacuums and that. Oh, is that a cathode tube? Yeah. Yeah, like the best amps are still made with vacuum tubes.

24:34You can get solid state amps, but the sound isn't as rich. So it's kind of like this old technology that's still superior.

24:40Chuck Bryant:Right, they're all pumped out by hand by a 90-year-old man in Tennessee. Mr. Marshall. Yes. No. So the cathode is a heated filament just like you might see in a light bulb. and the machine's going to pass a current through that and heat that thing up and then it's going to spit electrons off that surface and it's going to hit a disc made of tungsten and it's going to draw those across a tube. It's basically the tube is sort of the key piece. Right, because you've got the positive and the negative charge, the cathode and the anode, right? Yeah. And that difference, that electrical charge, draws those electrons down to the anode Yeah, with a lot of force.

25:23Chuck Bryant:Yeah, and that force means that when those electrons hit the tungsten anode, it knocks a bunch of electrons off, creates a bunch of x-rays in the process, and you have a whole box filled with x-ray radiation. A box full of x-rays. That's exactly what it is. I mean, there might as well be like a foot crank to this thing, like an old sewing machine for as technologically advanced as it is. There may be, for all I know. I don't know what goes on in that other room. Right, yeah, true. There's some dude in there with like, his right leg is three times more muscular than his left leg, because that's the only one he uses.

26:04Chuck Bryant:So in addition, like I said, to x-rays being created, the other x-rays, other photons can go on and knock more electrons off. So you have what's like a process of chain reaction starting, right? It's not like one gets hit and then that's it and a photon's created and it just hangs around until it's beamed out. Like you're just generating this huge amount of x-rays and the x-rays are also continuing to propagate themselves because they're knocking more electrons free. And the more free electrons you have, the more interactions you have, right? Right. So one of the ways that more electrons can be knocked off, you don't even need a direct transfer of energy where a photon is absorbed or knocks an electron from one orbit to another or knocks it loose entirely.

26:48Chuck Bryant:a photon actually has this really cool capability of just orbiting close by the nucleus of an atom. And when the nucleus basically draws it into its orbit, the photon just takes a hard left turn. Yeah, just bumps it off its course. But even like the Dodge Viper has to slow down to take a left turn, slow a little bit, right? Just a little. Just a little. Yeah. But that little bit in the photon world means a transfer of energy from the photon outward. Yeah, as an x-ray. Yeah, and then the photon takes that left turn and the energy is transferred to the atom. Yeah, and one of the byproducts, if this sounds like it's going to create a lot of heat, it's because it will.

27:36And in order to combat this, they rotate this anode to keep it, it would just melt down if you kept it in place. Yeah. And apparently there's a cool oil bath that helps absorb heat as well, which I never have heard of that either.

27:49Chuck Bryant:It sounds oily. A cool oil bath? Yeah, it doesn't sound refreshing at all. It sounds like the opposite of refreshing. Yeah, cool and oil don't really go together. No. Yeah. And I misspoke. That's an electron that can be drawn to the nucleus of an atom appropriately enough because they orbit nuclei anyway. Right. But it doesn't have to hook up with that atom. When it takes that hard left, it emits the photon like you said. That's right. And like I said earlier, there's a camera on the other side of the patient and it's going to record that pattern of light when it passes through the body. And it's not so different from a regular camera.

28:24And in the end, you're just going to get a picture, like I said, a negative image.

28:28Chuck Bryant:Yeah, and if you hook it up with a computer, that allows you to take x-rays basically in slices. You can come up with computerized tomography. Yeah, a.k.a. CT, a CT scan. Exactly. If you get a breast exam, you're using a type of x-ray called mammography. Yep. And then there's a fluoroscopy, which the man in the extraordinarily dry presentation from Siemens said was basically like moving picture video. It's like a movie. Exactly. And then he showed us what a movie is with a flip book, right? That old flip book trick. And if you listen to this podcast, I'm sorry. I just want to apologize for both of us.

29:10Chuck Bryant:Siemens guy. Oh, yeah. Hats off to you for doing that at all. Yeah. Because he's probably saying, well, at least I was correct in everything I said. Exactly. That's a good point, sir. But with fluoroscopy, it's basically like a movie, an x-ray movie. And you would do this to make sure a heart is beating correctly because you wanted to see it. but you have to have an additional instrument because as we've said, x-rays will pass through tissue like heart tissue and muscle tissue and blood vessels and all this stuff you want to get pictures of using an x-ray so you have to use something called a contrast media for it.

29:51Yeah, a contrast agent is basically more dense than the soft tissue so if you want to, let's say, swallow, it's usually like a barium compound if you want to examine like your blood vessels or your circulatory system uh you're sometimes they can inject that or you might drink it to see if you're doing like a gastrointestinal right like a gi tract yeah you're going to swallow that stuff yeah which i've never had to do i think my dad had

30:16Chuck Bryant:to do that yeah i don't think it's super pleasant i get the impression not too but my dad did as well yeah it's an old guy thing yeah so i should be getting one soon yeah uh and then it allows you to see a moving image, basically how that liquid is, if there's any blockage. There's all sorts of applications for it. Yeah, because that liquid has a high radiological density, which means that the x-rays don't just pass right through the tissue that it's being suspended in, like your blood vessels. It absorbs it for it. So you get a picture of your blood vessels, your circulatory system, which is pretty cool.

30:54Chuck Bryant:It's pretty clever. it's also extraordinarily elementary in principle. That's right. My dear Watson. And that single picture, I think we mentioned CT and mammography and all that and fluoroscopy, but the single picture is just called standard radiography and that's when you're taking a photo of your skull. Right. Or your lungs or your bones or your teeth. And so speaking of the lead apron thing, man, it's always made me kind of nervous. Like if the rest of my body has to wear a lead apron but you're shooting an x-ray into my head am I going to be okay well we'll answer that right after this message this is Jana Kramer from wind down with Jana Kramer hey quick question for the parents listening right now when's the last time your kid asked for something and you actually felt good saying yes because lately a lot of families have been hearing the same thing can I have lingo kids, please.

31:51Chuck Bryant:And here's the thing. Lingo kids is the number one entertainment platform for young kids with more than 4 ,000 interactive games, songs, and shows, astronauts, wild animals, superheroes, dinosaurs. It's literally everything kids love all in one place. So when they ask for it, you can actually feel good saying yes, download lingo kids for free and start exploring today or unlock even more amazing content with lingo kids plus. And if you go with the yearly plan, you can save up to 60%. Search Lingo Kids in the App Store or Google Play. Lingo Kids, everything kids love. Ready to finally clean out your closet?

32:30With Trashy, you can donate your clothes, reduce waste, and earn cash rewards all in one simple step. Just fill a take-back bag, send it in, and get rewards cash back for every bag. And now with Trashy Unlimited, you get unlimited bags for just$48 your first year. Clean out, donate, earn rewards. Visit Trashy.io to get started. Hey everyone, it's Cal Penn. I'm the host of Ear Say, the Audible and iHeart Audiobook Club. This week on the podcast, I am sitting down with Ray Porter, the narrator of Andy Weir's audiobook project Hail Mary, massive sci-fi adventure about survival and science and what happens when you wake up alone very far from earth.

33:21I really had to make a decision because I caught myself getting that frog in my throat and starting to get teary as I'm narrating some of these sections and it's like,

33:29Chuck Bryant:okay, yo, yo, yo, is this indulgent? And I really thought about it. I was like, no, at this point it would kind of be betraying the trust the author and the listener have in telling this story if I don't go through it. But there's places in this book that deeply emotionally affected me, and I left it on the mic. That's great. Because it served the story. People will say like, oh my God, I cried at the end. It's like, yeah, dude, me too. Listen to Earsay, the Audible and iHeart Audiobook Club on the iHeartRadio app or wherever you get your podcasts. Stuff you should know All right, x-rays, are they bad for you?

34:09The answer is yes, pretty unequivocally. But like all things, it's in moderation is the key. Sure. In the 1930s and 40s and into the 50s, they had x-ray machines at shoe stores. Oh, yeah. They could x-ray your feet to get a better fit. And they didn't realize at the time that they were x-raying people way, way too much.

34:32Chuck Bryant:You had talkative kids in class. they'd just shoot him with an x-ray? Would they? No. They probably did. I've got you like twice today. Well, no, I believe that. Like, hey, let's look at his brain. There may be a mouse running around inside of it. People in the 30s were dumb. Well, it's basically radiation sickness. It's a form of ionization, or ionizing radiation. Right. So what can happen, like if just normal light hits an atom, it's no big deal, but when an x-ray hits an atom, it knocks electrons off of it, creates an ion, which is an electrically charged atom. And basically anything from cellular death to mutation can happen at that point.

35:12And mutation can spread and it can cause cancer.

35:15Chuck Bryant:Right, because stable atoms are neutral, right? Because they have an equal number of protons and electrons. You lose an electron, all of a sudden you have a positively charged ion and that negatively charged electron running around and it just causes trouble. And you said light, visible light, can be absorbed and it's no big deal because visible light exists on a wavelength that's about in tune with the soft tissues of our body, right? So we know how to absorb it and it makes us tan and that's cool, right? But with these ionized atoms, these positively charged atoms going around in your body, it can cause a lot of problems like mutations, like cancer, right?

35:56Yeah, I mean if you break that DNA chain, that's not good. No, it isn't.

36:00Chuck Bryant:And one of the results is the DNA can basically lose its ability to regulate itself, and the cell replicates more frequently than it should, and all of a sudden you have a tumor on your hands, and that can spread. It can also be a problem if that DNA break occurs in utero, because then that can lead to birth defects, which is why pregnant women shouldn't get x-rays. And it can also just lead to plain old cellular death. If you have cellular death, then the tissues that are made up by those cells break down, and you have a problem on your hands with that as well. So here's the deal. We get exposed to radiation every day just walking around on the planet.

36:43Yeah. It depends on where you live, but every year the average person is going to be exposed to anywhere from one to four. It's measured in millisieverts per year, like I said, depending on where you are. I think in higher elevations, it's less than at sea level. So if you live in Denver, Colorado, you're going to be exposed to less.

37:04Chuck Bryant:Well, yeah, because you're higher up in the atmosphere, and that makes a difference. Exactly. You have less protection, right? Yeah. So what they want to do, medically speaking, they want to use, or they're supposed to use, the minimum amount to achieve the pictures you need. It's not like the old days where they're just like, let's do 20 x-rays. like let's do the minimum amount we need to get the information that we need a CT scan can get your you know you lay down in the tube and it rotates around you and your whole body can be photographed in less than five seconds these days but you know there are concerns if you get too many x-rays still like a dental panorama I think what does it say one to four millisieverts per year and it's cumulative too you should say Like it's not like you get one and then, you know, eight months later you get another one and that first one went away.

38:01Chuck Bryant:Like it accumulates over the course of a year. Yeah. So here's just a few examples of how much radiation you're being exposed to with x-rays. A dental panorama is going to be 0.01 millisieverts. So not very much. Like two chest x-rays might be 0.1. Mammogram is around 0.4. Your pelvis, 0.6. Your upper back may be 1.0. I wonder why. Because there's so much bone there? Maybe. Yeah, maybe it had to do with exposure to, yeah, that makes sense. I got a ton of bone in my upper back. A full CT scan, it depends on what you are, it depends on what you're x-raying, but a CT scan is obviously more like an abdominal or pelvis CT scan could be as many as 10 millisieverts.

38:54Yeah. So that's like up to two or three years worth of radiation in a single CT scan. Yeah. Which can be problematic, which is why they don't say get in the CT machine like every other week. Right. But, you know, some of the reasons you might, if you had a traumatic injury, they're going to x-ray you. A lot of times for disease confirmation, they'll use an x-ray machine. During surgery is a visual guide. Like if you do endoscopic surgery, the surgeon actually needs to look at something. So sometimes it was x-ray for that. Or to monitor your healing process, when you break a bone, it's not just that first x-ray.

39:32You're going to keep getting them to see how you're healing up.

39:34Chuck Bryant:This is right out of the Siemens video, huh? No. It isn't? Uh-uh. Oh, okay. I don't think so. I mean, I looked at so much stuff, it all runs together. I call it cumulative research. So I did a brain stuff on sieverts and how many we can take. And yeah, it's kind of like, it's a little alarming how much radiation we're exposed to. People who fly a lot, too, are exposed to tons of radiation because you're, again, higher up in the atmosphere, so you're less protected by the atmosphere. Speaking of flying, of course, baggage, that is x-rayed. The food industry uses x-rays a lot. Archaeologists use it if they don't want to destroy an object and they want to see what's inside.

40:17Or earth sciences, they'll use x-rays for rocks to see what kind of mineral composition. So there's all sorts of applications. It's not just medical. Space. Yeah. X-ray telescopes out on satellites. Yeah. Apparently you can see a lot. You can see things you can't detect from an earthbound telescope because X-rays are absorbed by our atmosphere, so you can't shoot it into space like that.

40:41Chuck Bryant:So this article makes a pretty good point, if you ask me. It says, like, yes, X-rays are bad for you, and you should use them with care and caution. And one good point is to always ask if there's an alternative to an x-ray. Just to basically say, hey, doc or dentist, slow your roll. Is there another way we can get this information without an x-ray? I know it's the easiest, but what are the alternatives? But then the article makes the point, it's still safer than the ultimate alternative, the thing that x-rays replaced, which was exploratory surgery. Yeah, back in the day, hey, if they thought you had cancer, they would cut you open and see.

41:20Yeah. And this is definitely better than that.

41:22Chuck Bryant:Yeah, or broken bone. Imagine getting that arm cut open just to see how it's doing. They're like, nope, it's not broken. Right. And we haven't invented anesthetic yet, so joke's on you. Good luck with your dentist, by the way, because I always get the feeling that the dentists are like, no, your insurance allows us to bill for so many per year. Right, exactly. So that's how many you're going to get. These x-rays are putting my kid through college. Yeah. You got anything else on x-rays? No. That was a fine amount of stuff. I'm feeling good about it. You feel good about this one? Sure. I do too.

41:56Chuck Bryant:If you want to know more about x-rays, you can check out this really informative article on HowStuffWorks.com. It's got some great diagrams that explain a lot of the stuff we were saying visually. And you can type x-ray into the search bar at HowStuffWorks and it'll bring that up. Since I said search bar, it's time for listener mail. This is from my buddy Poppy in Vancouver. Stuff You Should Know, a listener that I met while I was there. And Poppy, as this is to say, he's got a pretty cool job. He listened to the PTSD show and wanted to write in about another option that he works with. He's a registered acupuncturist in Vancouver with special training in trauma and addictions.

42:35He has a program called Neurotrophic Stimulation Therapy, NTSD, and a large part of the program uses ear acupuncture. and electroacupuncture to promote neuroplasticity in the brain. He says you can't necessarily directly fix the brain, but you can stimulate the ear nerves and will help the brain re-regulate certain functionalities so it can heal itself. He's been treating trauma and PTSD patients for several years, and the evidence for his efficacy is high. It can be done with acupuncture needles alone or in combination with a mild electrical stimulation. Remember we talked about...

43:12Chuck Bryant:Transcranial electromagnetic stimulation? Yeah, transdermal cranial stimulation. He says that's one of the things that he's also using to treat PTSD, which is pretty cool. Wow. And he said it makes cognitive behavioral therapies so much easier to introduce because it promotes neuroplasticity, and the results help a PTSD sufferer to be more open to and able to receive positive social programming. So here's a program we want to promote. If you want to see all the components in action in this program, you can visit Last Door Recovery Society at lastdoor.org slash ntst. Or you can donate funds to help purchase a brain scanner so that they can scientifically measure the results of the program, which would really help show the validity of the therapies.

43:55And if you're interested in helping out Poppy's cause there, because he's really big on treating veterans in Canada and the U.S., I shortened his little URL to bit.ly, B-I-T dot L-Y slash one one Y-N-L-O-Q. And that is from Poppy, and he says, Namaste.

44:16Chuck Bryant:Thanks a lot, Poppy. Is it Poppy with an O? P-O-P-P-I. Nice. If you want to get in touch with us, you can tweet to us at SYSK Podcast. You can join us on Facebook.com slash StuffYouShouldKnow. You can send us an email to stuffpodcast at howstuffworks.com That's right And as always join us at our home on the web Stuffyoushouldknow.com

44:44For more on this and thousands of other topics Visit howstuffworks.com

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